Biodiesel is a non-petroleum-based fuel made from renewable resources, for example, plants, microorganisms, or the like. It can be used as a diesel fuel substitute or as a component of fuel blends. Biodiesel is biodegradable and non-toxic, so fuel spills pose far less risk to the environment. Further, because the production of biodiesel “recycles”CO2, biodiesel production and use does not significantly contribute to global warming.
Biofuels, and in particular biodiesel, are now produced in many countries as alternatives to petroleum products. Biodiesel is usually produced from a variety of oils, such as vegetable oils or recycled fryer oils, and waste animal fat. Biodiesel may be used alone or in mixture with petroleum diesel to fuel all types of vehicles equipped with diesel engines including trucks, locomotives, industrial equipment, private cars and boats. Biodiesel use reduces greenhouse gas emission and consequently many governments have promoted it through tax exemption and other various incentives. Therefore, several biodiesel production plants have been built throughout the world and more are planned to enter into production in the next few years.
Chemically, biodiesel feedstock can be composed primarily of transesterifiable lipids, including for example glycerides, which are formed from a single molecule of glycerol with one to three long chain fatty acids attached.
Biodiesel can be produced by direct transesterification of such lipids (including mono-, di-, or triglycerides) from an oil or a fat with an alcohol, often methanol, in presence of an acidic or basic catalyst:

Several acidic or basic catalysts are known to be useful for this reaction.